Currently, manganese cells, alkaline cells, and so on have been used as electric power sources of a wide variety of portable electric devices such as handheld personal computers, personal digital assistants (PDAs), and cellular phones. Typically, each of these cells comprises: a negative electrode made of zinc; and a positive electrode made of manganese, with an electromotive force of 1.5 volts. As the portable electric devices became more advanced, the improvements in high voltage, high capacity, and lightweight characteristics of primary or secondary cells have been demanded.
In contrast, it has been expected that the improvements in high voltage, high capacity, and lightweight characteristics of such primary cells would be easily attained, compared with those of the primary cells using the negative electrodes made of zinc. Thus, the primary cells using negative electrodes made of aluminum have been investigated and developed for a long time. Among the prior art technologies, for example, U.S. Pat. No. 2,838,591 (1958) discloses a primary cell comprising a positive electrode containing manganese dioxide, a negative electrode made of aluminum, and an electrolyte consisting of a weak-acid aqueous solution of aluminum chloride. In this case, however, the aluminum employed in the negative electrode tends to react with the electrolyte, so that there are several problems of generating a gas as a reaction product and increasing the amount of self-discharge. Moreover, it is demanded that a primary cell of a high output by which a larger amount of current can be obtained as compared with that of using a weak-acid aqueous solution of aluminum chloride as an electrolyte.